Bill Gross, who runs the world’s biggest bond fund at Pacific Investment Management Co., said economies and their financial markets take decades to normalize after the havoc of a debt crisis, making U.S. securities still the safest bet for investors.

For the past two years, investors have feared a contagion of default, triggered by a loss of liquidity and a panic among bankers and other bond investors, something akin to what happened in the United States during the subprime crisis.